1. Technical Field
The present invention relates to an opthalmological apparatus for breakdown of eye tissue. The invention relates in particular to an opthalmological apparatus that comprises a base station with a light source for generating light pulses, an application head that can be mounted on the base station by means of a support arm and can be placed onto the eye, with a light projector for focused projection of the light pulses, and an optical transmission system for transmitting the light pulses from the base station through the support arm to the application head.
2. Related Art
Instances of ametropia such as myopia (short-sightedness), hyperopia (long-sightedness or far-sightedness) or astigmatism can nowadays be permanently corrected by refractive surgical treatment. Refractive surgical treatments are surgical operations on the eye which change the optical refractive power of the eye with the aim of bringing it as close to a desired value as possible. One of the most important methods in refractive surgery is so-called laser-assisted in situ keratomileusis (LASIK) in which the interior of the cornea is removed with the aid of a computer-controlled excimer laser after a corneal flap has previously been partially severed and folded aside. To produce the corneal flap, use is made of mechanical microkeratomes in which a driven scalpel cuts the corneal flap. Recently, such corneal flaps have also been cut with the aid of strongly focused femtosecond laser pulses, which have pulse widths of typically 100 fs to 1000 fs (1 fs=10−15 s). In addition to LASIK, there are further procedures for refractive correction that are performed on the cornea with the aid of femtosecond lasers. Such a system is marketed, for example, by IntraLase Corp, in Irvine, Calif., USA under the name of Pulsion FS Laser. In this system, a light source (femto laser) is located in a base station and is connected to an optical application head via an articulated mirror arm. In addition to the optical transmission system, a deflection system (scanner) and the light projector, the application head also comprises viewing means, such as camera or surgical microscope, and therefore has a considerable weight of several kilograms. For orienting and applying the light projector onto an eye of a patient, the entire application head is moved via linear translatory drives. The patient lies on a bed and does not move. For reasons of weight, the application cannot be done by hand, and motorized drives are necessary. To avoid applying excessive forces to the patient, the laser system comprises force-measuring systems in the vertical application direction.
Systems for cutting the corneal flap with focused femtosecond laser pulses are also marketed by Zeiss Meditec AG, with its Visumax, and by 20/10 Perfect Vision Optische Geräte GmbH, with its Femtec. In these systems, the light projector is connected fixedly to the base station. In these systems, the patient is oriented in the horizontal plane and also vertically with respect to the light projector with the aid of a patient bed. Therefore, these systems too cannot be applied manually onto the patient's eye. In addition, the special patient bed has to be integrated into the safety system of the laser system in order to avoid uncontrolled movements of the bed. The bed is thus part of the laser system and thus increases the system costs and the space required. A suitable choice of bed by the person using the system is not possible.
In the aforementioned systems, the docking of the light projector onto the patient's eye is first effected by orientation in the horizontal plane in the x-direction and y-direction (centring of the eye) and then by lowering or lifting the patient in the vertical z-direction.
EP 1731120 describes a system in which the application head is mounted flexibly on the base station via an articulated mirror arm composed of several arm elements and joints and permits manual application of the application head and light projector onto the eye of a patient. To permit the weight of the application head for manual application by means of the articulated mirror arm, the light projector has smaller lens systems compared to the previously known systems. In order to ensure that, despite the lens system of smaller dimensions, it is possible to work with focused laser pulses across an extensive work area on the eye, the application head additionally has movement drivers for moving the light projector in an advance direction and in a first scanning direction. An optical deflection to a vertical scanning direction is not possible, however. The limited work area permits only rapid positioning of the laser pulses within the work area. Limits are thus set on flexible positioning of the laser pulses across the entire eye.